Standard leptogenesis assumes that \(CP\)  violation and the violation of \(B\!-\!L\)  occur simultaneously, namely, whenever the RHN interactions are active in the thermal bath.
In Ref. [1]}, we, however, recently pointed out that this is, in fact, not a necessary condition in scenarios beyond the Standard Model (BSM) that include heavy Majorana neutrinos.
In BSM models that build upon the type-I seesaw extension of the Standard Model rather than the Standard Model itself, there may, instead, exist a large hierarchy between the temperature scales of \(CP\)  and \(B\!-\!L\)  violation, which significantly relaxes Sakharov's conditions for successful baryogenesis [2]} and thus opens up a new window for model building.
The key observation in Ref. [1]} was that new \(CP\) -violating interactions at high energies can readily lead to the generation of primordial charge asymmetries, which are then converted by RHN interactions at lower energies to a new chemical equilibrium that features nonzero \(B\!-\!L\) .\(1\endcsname \)See also Refs. [4]}, [5]}, [6]}, [7]} for related earlier work as well as Refs. [8]}, [9]} for some related discussions in the more recent literature.

This mechanism, which we dubbed wash-in leptogenesis no longer relies on any \(CP\)  violation in the RHN sector, but merely utilizes RHN interactions in or close to thermal equilibrium in order to modify the chemical transport in the SM plasma.
Wash-in leptogenesis is thus based on the assumption that, just like the theoretical discovery of the weak sphaleron in the 1980s necessitated a first revision of the SM chemical transport, the experimental discovery of neutrino oscillations now calls for a second revision:
RHN interactions should be treated on the same footing as weak sphaleron processes; just like weak sphalerons can wash in a baryon asymmetry in the standard leptogenesis scenarios, RHNs can wash in a \(B\!-\!L\)  asymmetry.
